The objective of this research is to investigate the relationship between various forms of hypertension in the rat and corticoid (aldosterone) receptors located in smooth muscle cells grown from the rat aorta. These cells, grown by standard tissue culture techniques, contain two corticoid receptors which bind aldosterone. The first seems to bind salt retaining steroids; the second, glucocorticoids. An assay for these receptors has been established using gel exclusion chromatography to separate bound and free. Next, they will be characterized by pH sensitivity, temperature sensitivity, Sephacryl S 300 chromatography, glycerol gradient ultracentrifugation, and DEAE ion exchange chromatography. Control animal corticoid receptor characteristics will be compared to those in various forms of genetic hypertension (salt sensitive and spontaneously hypertensive rats) and genetic resistance to hypertension (Fischer 344 and Long-Evans rats). The effect of hypertension on the receptor will be assessed by characterizing the receptor found in Spraque-Dawley rats which are made hypertensive by a variety of techniques including saline loading, saline plus DOCA, Goldblatt procedure and adrenal regeneration. Corticoids may affect vascular smooth muscle cell regulation of blood pressure by causing the accumulation of water and electrolytes in the cells of the artery wall during the development of hypertension. This accumulation of water and electrolytes causes the cells to swell, narrows the lumen of the vessels, stiffens the vessels, and increases the peripheral resistance. Or, corticoids may affect the sensitivity of the arterial smooth muscle cells to catecholamines. Both of these possibilities will be investigated and correlations with receptor occupancy by the corticoid will be done. Lastly, the receptor-aldosterone complex will be used in a radioreceptor assay to screen other steroids for possible action upon the vascular smooth muscle cell. The ultimate goal of the research is the elucidation of the relationship between hypertension in the rat and the aortic corticoid receptors with a resultant increased understanding of hypertension in both rat and man.